The invention relates to the specific field of preserving over a period of time foods and provisions which have been subjected to cooking or pre-cooking, and is applicable in particular, but not exclusively, to food preserving processes used in the provision of public catering, for example in restaurants, canteens and the like, supermarkets, public catering services and military catering.
At the present time, the preserving of cooked or pre-cooked food takes place in various ways, according to the required preservation time.
In a first preserving procedure, freezing is carried out if the required preservation time is reckoned in days or weeks.
In a second preserving procedure, the food is refrigerated (at 4° C., for example) if the preservation time is a few days.
In another procedure, the food is preserved in the hot state in equipment for maintaining the temperature (at 70° C., for example) if the required time is several hours.
In yet another procedure, preserving is carried out at ambient temperature if the cooked food is to be consumed immediately or within a few hours of cooking.
There are also known procedures for preserving food in a modified atmosphere, for example by keeping ready-to-use lightly processed products (such as grilled vegetables) for a few days in a refrigerator.
In the first two procedures of freezing and refrigeration, the use of the cold chain gives rise to numerous problems. A first limitation is due to the fact that the food has to be brought to a relatively high temperature before serving, and therefore considerable periods of time are required.
Furthermore, these procedures require a number of treatments, because the food has to be initially cooled and then brought back to the serving temperature, resulting in high costs.
In preservation using a cold chain, the organoleptic characteristics of the food are also frequently compromised to a greater or lesser extent, as a result of thermal and mechanical stresses (particularly during the freezing process) and because of bacterial action, which is reduced but not eliminated.
The cold chain also has a high specific energy requirement for the three essential steps of temperature reduction, preserving, and regeneration at the serving temperature.
In the last two procedures mentioned, in which preservation is carried out at ambient temperature and/or in a modified atmosphere, the preservation time is also limited to a few hours because, at these temperatures, bacterial action and the degradation of the organoleptic characteristics is very rapid.
In many cases it may be found that the ideal preservation time is several days, for example in catering, where the cycle is typically weekly.